Method and system for beam expansion in a display device

ABSTRACT

An exit pupil extender with one input optical element and two exit optical elements disposed on different sides of the input optical element. The exit pupil extender also comprises two intermediate optical couplers, each disposed between the input optical element and one exit optical element. The couplers serve as exit pupil extending components. All optical elements and couplers are diffractive optical elements having grating lines. The grating lines of one optical element are substantially parallel to that of other optical elements, but the grating lines of the couplers are at substantially a 60-degree angle from that of the optical elements in order to optimize the exit pupil extending efficiency.

FIELD OF THE INVENTION

The present invention relates generally to a display device and, more specifically, to a display that uses two or more diffractive elements for extending the exit pupil of the display for viewing.

BACKGROUND OF THE INVENTION

While it is a common practice to use a low-resolution liquid-crystal display (LCD) panel to display network information and text messages in a mobile device, it is preferred to use a high-resolution display to browse rich information content of text and images. A microdisplay-based system can provide full color pixels at 50-100 lines per mm. Such high-resolution is generally suitable for a virtual display. A virtual display typically consists of a microdisplay to provide an image and an optical arrangement for manipulating light emerging from the image in such a way that it is perceived as large as a direct view display panel. A virtual display can be monocular or binocular.

The size of the beam of light emerging from imaging optics toward the eye is called exit pupil. In a Near-Eye Display (NED), the exit pupil is typically of the order of 10 mm in diameter. Further enlarging the exit pupil makes using the virtual display significantly easier, because the device can be put at a distance from the eye. Thus, such a display no longer qualifies as an NED, for obvious reasons. Head-Up Displays are examples of the virtual display with a sufficiently large exit pupil.

WO 99/52002 discloses a method of enlarging the exit pupil of a virtual display. The disclosed method uses three successive holographic optical elements (HOEs) to enlarge the exit pupil. In particular, the HOEs are diffractive grating elements arranged on a planar, light transmissive substrate 6, as shown in FIG. 1. As shown, light from an image source 2 is incident upon the first HOE, or H1, which is disposed on one side of the substrate 6. Light from H1, coupled to the substrate 6, is directed toward the second HOE, or H2, where the distribution of light is expanded in one direction. H2 also redirects the expanded light distribution to the third HOE, or H3, where the light distribution is further expanded in another direction. The holographic elements can be on any side of the substrate 6. H3 also redirects the expanded light distribution outward from the substrate surface on which H3 is disposed. The optical system, as shown in FIG. 1, operates as a beam-expanding device, which maintains the general direction of the light beam. Such a device is also referred to as an exit pupil extender (EPE).

In an EPE, the energy of the exit beam relative to the input beam depends upon the coupling between adjacent optical elements. As the energy output of the image source is limited, it is desirable to achieve a high coupling efficiency between adjacent optical elements.

It is advantageous and desirable to provide a method and system for improving the optical coupling between optical elements in an exit pupil extender.

SUMMARY OF THE INVENTION

It is an objective of the present invention to improve the optical coupling between two optical elements such as diffractive optical elements in an exit pupil extender. This objective can be achieved by using a diffractive optical element having the grating lines are oriented in a certain direction as optical coupler disposing between the input optical element and the exit optical element. In particular, the grating lines of the optical coupler are oriented substantially at a 60-degree from the grating lines of the input and exit optical element.

Thus, the first aspect of the present invention provides an optical device, comprising:

a substrate of optical material having a first side and an opposing second side;

a first diffractive element disposed on the substrate for receiving a light beam;

a second diffractive element disposed on the substrate in relationship with the first diffractive element; and

an intermediate diffractive element disposed between the first and the second diffractive elements, wherein

at least part of the received light beam is diffracted in the first diffractive element for providing a diffracted light component to the intermediate diffractive element in an incident direction substantially within the first and second surface, and

at least part of the diffracted light component in the intermediate different element is coupled to the second diffractive element substantially between the first and second surfaces so as to allow at least part of the coupled diffracted light component to exit the substrate by diffraction in the second diffractive element, wherein the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction for producing conical diffraction.

According to the present invention, the angle in the conical diffraction is between 50 and 70 degrees.

According to the present invention, the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction so that the incident direction of the diffracted light component provided to the intermediate different element is within an angular range between 20 and 40 degrees relative to the pattern direction.

According to the present invention, the optical device further comprises:

a third diffractive element disposed on the substrate in relationship with the first diffractive element spaced from the second diffractive element; and

a further intermediate diffractive element disposed between the first and the second diffractive elements, wherein

at least part of the received light beam is diffracted in the first diffractive element for providing a diffracted light component to the further intermediate diffractive element in an incident direction within the first and second surface, and

at least part of the diffracted light component in the further intermediate different element is coupled to the third diffractive element substantially between the first and second surfaces so as to allow at least part of the coupled diffracted light component to exit the substrate by diffraction in the third diffractive element, wherein the further intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction such that the incident direction of the diffracted light component provided to the further intermediate different element is within an angular range between 50 and 70 degrees relative to the pattern direction.

According to the present invention, the received light beam is received in the first diffractive element through the first surface and at least part of the coupled diffracted light component exits the substrate through the first surface or the second surface.

According to the present invention, intermediate diffractive element comprises a plurality of grooves forming the period pattern.

According to the present invention, the first diffractive element has a period pattern composed of a plurality of linear elements along a pattern direction substantially perpendicular to the incident direction, and the second diffractive element has a period pattern composed of a plurality of linear elements along a pattern direction substantially perpendicular to the incident direction.

The second aspect of the present invention provides a method of optical coupling in an optical device, the optical device comprising:

a substrate of optical material having a first side and an opposing second side;

a first diffractive element disposed on the substrate for receiving a light beam, wherein at least part of the received light beam is diffracted in the first diffractive element for providing a diffracted light component; and

a second diffractive element disposed on the substrate in relationship to the first diffractive element so as to allow at least part of the diffracted light component to exit the substrate substantially by diffraction in the second diffractive element. The method comprises:

disposing an intermediate diffractive element between the first and the second diffractive elements, so as to allow part of the diffracted light component to enter the intermediate diffractive element between the first and second surfaces at an incident direction, wherein the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction to produce conical diffraction.

According to the present invention, the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction such that the incident direction of the diffracted light component is within an angular range between 20 and 40 degrees relative to the pattern direction.

According to the present invention, the optical device further comprises a third diffractive element disposed on the substrate in relationship to the first diffractive element spaced from the second device so as to allow at least part of the diffracted light component also to exit the substrate substantially by diffraction in the third diffractive element. The method further comprises:

disposing a further intermediate diffractive element between the first and the third diffractive elements, so as to allow part of the diffracted light component to enter the further intermediate diffractive element between the first and second surfaces at an incident direction, wherein the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction such that the incident direction of the diffracted light component is within an angular range between 50 and 70 degrees relative to the pattern direction.

According to the present invention, the first diffractive element has a substantially period pattern composed of substantially linear elements along a first pattern direction, and the second diffractive element has a substantially period pattern composed of substantially linear elements along a second pattern direction substantially parallel to the first pattern direction.

The third aspect of the present invention provides an electronic device comprising:

a data processing unit;

an optical engine operatively connected to the data processing unit for receiving image data from the data processing unit;

a display device operatively connected to the optical engine for forming an image based on the image data; and

an exit pupil extender, comprising:

-   -   a substrate of optical material having a first side and an         opposing second side;     -   a first diffractive element disposed on the substrate for         receiving a light beam;     -   a second diffractive element disposed on the substrate in         relationship with the first diffractive element; and     -   an intermediate diffractive element disposed between the first         and the second diffractive elements, wherein     -   at least part of the received light beam is diffracted in the         first diffractive element for providing a diffracted light         component to the intermediate diffractive element in an incident         direction substantially within the first and second surface, and     -   at least part of the diffracted light component in the         intermediate different element is coupled to the second         diffractive element substantially between the first and second         surfaces so as to allow at least part of the coupled diffracted         light component to exit the substrate by diffraction in the         second diffractive element, wherein the intermediate diffractive         element has a substantially periodic pattern composed of         substantially linear elements along a pattern direction for         producing conical diffraction.

According to the present invention, the angle in the conical diffraction is between 50 and 70 degrees, and the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction so that the incident direction of the diffracted light component provided to the intermediate different element is within an angular range between 20 and 40 degrees relative to the pattern direction.

According to the present invention, the optical device further comprises:

a third diffractive element disposed on the substrate in relationship with the first diffractive element spaced from the second diffractive element; and a further intermediate diffractive element disposed between the first and the second diffractive elements, wherein

at least part of the received light beam is diffracted in the first diffractive element for providing a diffracted light component to the further intermediate diffractive element in an incident direction within the first and second surface, and

at least part of the diffracted light component in the further intermediate different element is coupled to the third diffractive element substantially between the first and second surfaces so as to allow at least part of the coupled diffracted light component to exit the substrate by diffraction in the third diffractive element, wherein the further intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction such that the incident direction of the diffracted light component provided to the further intermediate different element is within an angular range between 50 and 70 degrees relative to the pattern direction.

According to the present invention, the electronic device can be a portable device, such as a mobile phone, personal digital assistant (PDA), communicator, portable Internet appliance, hand-held computer, digital video and still camera, wearable computer, computer game device, specialized bring-to-the-eye product for viewing and other portable electronic devices. However, the exit pupil extender, according to the present invention, can also be used in a non-portable device, such as a gaming device, vending machine, band-o-matic, and home appliances, such as an oven, microwave oven and other appliances and other non-portable devices.

The present invention will become apparent upon reading the description taken in conjunction with FIGS. 2-7.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation showing a prior art exit pupil extender using three diffractive elements.

FIG. 2 is a schematic representation showing a top view of an exit pupil extender, according to the present invention.

FIG. 3 a schematic representation showing an isometric view of the exit pupil extender, according to the present invention.

FIG. 4 is a schematic representation showing the orientation of the grating lines in the intermediate diffractive optical element, according to the present invention.

FIG. 5 is a schematic representation showing another embodiment of the exit pupil extender, according to the present invention.

FIG. 6 is a schematic representation showing typical reflection and diffraction in a diffractive optical element.

FIG. 7 is a schematic representation showing an electronic device, having a virtual display system.

DETAILED DESCRIPTION OF THE INVENTION

In the exit pupil extender (EPE) 10, according to the present invention, has a substrate 20 made of an optical material. On the substrate 20, there are one input optical element 30 and one or two exit optical elements 50, as shown in FIG. 2. The EPE 10 also has one or two intermediate optical couplers 40, 40′ each disposed between the input optical element 30 and one of the exit optical elements 50, 50′. The couplers 40,40′ serve as exit pupil extending components. The optical elements 30, 50, 50′ and the couplers 40, 40′ are diffractive optical elements (DOEs), for example. Each of the DOEs has a plurality of grating lines for diffraction purposes. As shown, the optical element 30 has a plurality of grating lines 32; the optical element 40 (40′) has a plurality of grating lines 42 and the optical element 50 (50′) has a plurality of grating lines 52.

FIG. 3 is an isometric view showing the relationship between an input beam 70 and two exit beams 80, 80′. As shown, the substrate 20 has a first side 22 and a second side 24. The input beam 70 enters the EPE 10 on one side of the substrate 20 and exit beams 80, 80′ exit the EPE 10 on a different side of the substrate 20, in a direction substantially parallel to the input beam.

As shown in FIG. 2, the grating lines 32 and 52 in DOEs 30 and 50 (50′) are substantially parallel to the Y-axis. In order that the DOE 40 (40′) acts like a beam extender, and that its efficiency is optimized, the grating lines in the coupler DOEs 40 (40′) are substantially at a 60-degree angle in reference to the Y-axis, as shown in FIG. 4. As such, the light entering one side of the DOEs 40 (40′) is trapped in the grating area between the first side 22 and the second side 24 until it emerges out from the other side of the DOEs 40 (40′). Furthermore, the shape of the DOEs 40 (40′) is designed so that, at the output end, the rays leaving the grating area are substantially parallel to the X-axis, as shown in FIG. 3.

According to one embodiment of the present invention, the grating periods in all DOEs 30, 40 (40′) and 50 (50′) are substantially the same. However, while the DOE 30 and 50 (50′) have the same period, the DOE 40 is allowed to deviate from those slightly without disturbing the functioning of the EPE system. Nevertheless, each of the gratings has a unique grating profile, optimized to its function. DOE 30 and DOE 40 (40′) typically have a deep profile and a proper filling ratio.

As shown in FIG. 3, when the EPE 10 is used to expand a light beam 70 incident upon the DOE 30, the beam 70 is diffracted and reflected, due to total internal reflection (TIR) on one side of substrate 20 (if the DOE 30 is disposed on the upper side 22, then TIR occurs on the lower side 24) toward the DOEs 40 (40′) substantially along the direction 72 (72′). The beam is further diffracted from the DOEs 40 (40′) to the direction that makes substantially a 60 degree conical angle with respect to the direction 72 (72′). After a TIR in the lower side of the substrate 20, the beam encounters the grating 40 (40′) again and then is diffracted again in a direction parallel to direction 72 (72′). Finally, after some successive steps, the beam enters the DOEs 50 (50′) substantially along the direction 74 (74′), which is substantially the same as direction 72 (72′). It is important to ensure that the beam encounters the grating 40 (40′) an even number of times. Otherwise the beam does not enter DOE 50 (50′) exactly at the correct direction. Finally, the beam exits the DOEs 50, 50′ as exit beams 80, 80′. It should be noted, however, that the cross section of the exit beams 80, 80′ is larger than that of the input beam 70 as the input beam is expanded in the DOEs both in the Y and X axes. As shown in FIG. 3, the incident angle of the light beam entering the DOE 40 is substantially along the direction 72, which is substantially in the XZ plane. The direction 72 can be calculated from the conical grating equations, and generally in practical cases, the beam in the direction 72 does not exactly travel in the XZ plane, but deviates some degrees from that.

FIG. 4 shows the orientation of the grating lines 42 in the DOE 40. As mentioned above, the grating lines 42 are substantially at a 60-degree angle in reference to the Y-axis. Thus, the grating lines 42 are substantially at a 60-degree conical angle in reference to the incident direction 72 (see FIG. 3). However, the conical angle can deviate from 60 degrees as long as in the diffraction there exists only two reflected diffraction modes, zero and first order. It should be noted that, in conical diffraction, the beam is, in general, not perpendicular to the grating lines. The conical angle is defined from the perpendicular position. This condition depends on the incoming beam angles (70), grating period and on the refractive index of the material. This acceptable angular space must be calculated case by case using the conical diffraction formulas. This acceptable angular space is generally so large, that the system works in most of the practical cases, even wide field of view cases. As mentioned earlier, it is necessary that the beam meets an even number of times the grating 40 (40′). Therefore the angle of the leaving edge of the DOE 40 (40′) must be such that this condition is fulfilled. This angle can be calculated from the conical diffraction formulas and the angular spread of the incoming beams. Generally, the leaving edge of DOE 40 (40′) thus forms an angle slightly larger than 30 degrees with respect to the Y-axis. The DOE 40 (40′) is typically a binary type grating and, in the geometry described in this invention, the diffraction efficiency of the first diffraction order can be as high as 90%. Furthermore, the grating efficiency can be tuned to be polarization independent with a proper filling ratio.

The DOE 40′ is substantially a mirror image of the DOE 40. Thus, the orientation of the grating lines 42′ is similar to that of the grating lines 42.

As shown in FIG. 3, the input beam 70 entering the DOE 30 on one side of the EPE 10, while the exit beams 80, 80′ leave the DOE 50, 50′ on the other side of the EPE 10. It should be noted that generally arrangement of the diffraction gratings in the EPE 10 is such that the exit beams 80 and 80′ exit the EPE 10 also on the same side as the input beam 70 entering the EPE 10, as shown in FIG. 5.

It is known in the art that the beam expansion in the exit beams 80, 80′ as compared to the input beam 70 is partly due to the different dimensions and shapes in the various DOEs, and partly due to the multiple diffraction and total internal reflection (TIR). As shown in FIG. 6, the incoming beam is reflected by TIR at different locations R and diffracted by the grating lines 52 at diffraction locations D, resulting in the exit beam 80.

The EPE 10 can be used in a portable device 100, such as a mobile phone, personal digital assistant (PDA), communicator, portable Internet appliance, hand-hand computer, digital video and still camera, wearable computer, computer game device, specialized bring-to-the-eye product for viewing and other portable electronic devices. As shown in FIG. 7, the portable device 100 has a housing 210 to a house a communication unit 212 for receiving and transmitting information from and to an external device (not shown). The portable device 100 also has a controlling and processing unit 214 for handling the received and transmitted information, and a virtual display system 230 for viewing. The virtual display system 230 includes a micro-display or image source 192 and an optical engine 190. The controlling and processing unit 214 is operatively connected to an optical engine 190 to provide image data to the image source 192 to display an image thereon. The EPE 10, according to the present invention, can be optically linked to an optical engine 190.

It should be noted that each of the optical elements 30, 40, 40′, 50, 50′ can be diffractive optical elements having grating lines or a holographic diffractive optical element (HOE) having interference fringes. As the name suggests, a holographic diffraction element is holographically produced where at least two coherent light beams are used to produce the fringes. In contrast, a diffraction optical element can be mechanically or chemically produced.

The objective of the present invention is to achieve efficient optical coupling between the various DOEs in an EPE while the DOEs are sized and shaped and arranged for exit pupil expansion. The application for the EPE of the present invention is not limited to virtual displays. The selective reflection control in a planar waveguide (substrate 20), according to the present invention, can also be used in any application where optical beam expansion in one or more directions is required and light of different wavelengths is used. The diffractive elements are, in fact, optical couplers and light modulator devices for coupling light into the planar waveguide. Thus, the EPE 10, as shown in FIGS. 2 to 6, can be viewed as an optical device comprised of a planar waveguide and a plurality of optical couplers (or light modulator devices) disposed adjacent to or on the waveguide for light coupling and manipulating purposes.

The image source 192, as depicted in FIG. 7, can be a sequential color LCOS (Liquid Crystal On Silicon) device, an OLED (Organic Light Emitting Diode) array, an MEMS (MicroElectro Mechanical System) device or any other suitable micro-display device operating in transmission, reflection or emission.

Moreover, the electronic device 100 can be a portable device, such as a mobile phone, personal digital assistant (PDA), communicator, portable Internet appliance, hand-held computer, digital video and still camera, wearable computer, computer game device, specialized bring-to-the-eye product for viewing and other portable electronic devices. However, the exit pupil extender, according to the present invention, can also be used in a non-portable device, such as a gaming device, vending machine, band-o-matic, and home appliances, such as an oven, microwave oven and other appliances and other non-portable devices.

Thus, although the invention has been described with respect to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention. 

1. An optical device comprising: a substrate of optical material having a first side and an opposing second side; a first diffractive element disposed on the substrate for receiving a light beam; a second diffractive element disposed on the substrate in relationship with the first diffractive element; and an intermediate diffractive element disposed between the first and the second diffractive elements, wherein at least part of the received light beam is diffracted in the first diffractive element for providing a diffracted light component to the intermediate diffractive element in an incident direction substantially within the first and second surface, and at least part of the diffracted light component in the intermediate different element is coupled to the second diffractive element substantially between the first and second surfaces so as to allow at least part of the coupled diffracted light component to exit the substrate by diffraction in the second diffractive element, wherein the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction for producing conical diffraction.
 2. The optical device of claim 1, wherein angle in the conical diffraction is between 50 and 70 degrees.
 3. The optical device of claim 1, wherein the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction so that the incident direction of the diffracted light component provided to the intermediate different element is within an angular range between 20 and 40 degrees relative to the pattern direction.
 4. The optical device of claim 3, further comprising: a third diffractive element disposed on the substrate in relationship with the first diffractive element spaced from the second diffractive element; and a further intermediate diffractive element disposed between the first and the second diffractive elements, wherein at least part of the received light beam is diffracted in the first diffractive element for providing a diffracted light component to the further intermediate diffractive element in an incident direction within the first and second surface, and at least part of the diffracted light component in the further intermediate different element is coupled to the third diffractive element substantially between the first and second surfaces so as to allow at least part of the coupled diffracted light component to exit the substrate by diffraction in the third diffractive element, wherein the further intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction such that the incident direction of the diffracted light component provided to the further intermediate different element is within an angular range between 50 and 70 degrees relative to the pattern direction.
 5. The optical device of claim 1, wherein the received light beam is received in the first diffractive element through the first surface and at least part of the coupled diffracted light component exits the substrate through the second surface.
 6. The optical device of claim 1, wherein the received light beam is received in the first diffractive element through the first surface and at least part of the coupled diffracted light component exits the substrate through the first surface.
 7. The optical device of claim 1, wherein the intermediate diffractive element comprises a plurality of grooves forming the period pattern.
 8. The optical device of claim 1, wherein the first diffractive element has a period pattern composed of a plurality of linear elements along a pattern direction substantially perpendicular to the incident direction.
 9. The optical device of claim 1, wherein the second diffractive element has a period pattern composed of a plurality of linear elements along a pattern direction substantially perpendicular to the incident direction.
 10. A method of optical coupling in an optical device, the optical device comprising: a substrate of optical material having a first side and an opposing second side; a first diffractive element disposed on the substrate for receiving a light beam, wherein at least part of the received light beam is diffracted in the first diffractive element for providing a diffracted light component; and a second diffractive element disposed on the substrate in relationship to the first diffractive element so as to allow at least part of the diffracted light component to exit the substrate substantially by diffraction in the second diffractive element, said method comprising: disposing an intermediate diffractive element between the first and the second diffractive elements, so as to allow part of the diffracted light component to enter the intermediate diffractive element between the first and second surfaces at an incident direction, wherein the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction to produce conical diffraction.
 11. The method of claim 10, wherein the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction such that the incident direction of the diffracted light component is within an angular range between 20 and 40 degrees relative to the pattern direction.
 12. The method of claim 11, wherein the optical device further comprises a third diffractive element disposed on the substrate in relationship to the first diffractive element spaced from the second device so as to allow at least part of the diffracted light component also to exit the substrate substantially by diffraction in the third diffractive element, said method further comprising: disposing a further intermediate diffractive element between the first and the third diffractive elements, so as to allow part of the diffracted light component to enter the further intermediate diffractive element between the first and second surfaces at an incident direction, wherein the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction such that the incident direction of the diffracted light component is within an angular range between 50 and 70 degrees relative to the pattern direction.
 13. The method of claim 10, wherein the first diffractive element having a substantially period pattern composed of substantially linear elements along a first pattern direction, and the second diffractive element having a substantially period pattern composed of substantially linear elements along a second pattern direction substantially parallel to the first pattern direction.
 14. An electronic device comprising: a data processing unit; an optical engine operatively connected to the data processing unit for receiving image data from the data processing unit; a display device operatively connected to the optical engine for forming an image based on the image data; and an exit pupil extender, comprising: a substrate of optical material having a first side and an opposing second side; a first diffractive element disposed on the substrate for receiving a light beam; a second diffractive element disposed on the substrate in relationship with the first diffractive element; and an intermediate diffractive element disposed between the first and the second diffractive elements, wherein at least part of the received light beam is diffracted in the first diffractive element for providing a diffracted light component to the intermediate diffractive element in an incident direction substantially within the first and second surface, and at least part of the diffracted light component in the intermediate different element is coupled to the second diffractive element substantially between the first and second surfaces so as to allow at least part of the coupled diffracted light component to exit the substrate by diffraction in the second diffractive element, wherein the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction for producing conical diffraction.
 15. The electronic device of claim 14, wherein angle in the conical diffraction is between 50 and 70 degrees.
 16. The electronic device of claim 14, wherein the intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction so that the incident direction of the diffracted light component provided to the intermediate different element is within an angular range between 20 and 40 degrees relative to the pattern direction.
 17. The electronic device of claim 16, wherein the optical device further comprises: a third diffractive element disposed on the substrate in relationship with the first diffractive element spaced from the second diffractive element; and a further intermediate diffractive element disposed between the first and the second diffractive elements, wherein at least part of the received light beam is diffracted in the first diffractive element for providing a diffracted light component to the further intermediate diffractive element in an incident direction within the first and second surface, and at least part of the diffracted light component in the further intermediate different element is coupled to the third diffractive element substantially between the first and second surfaces so as to allow at least part of the coupled diffracted light component to exit the substrate by diffraction in the third diffractive element, wherein the further intermediate diffractive element has a substantially periodic pattern composed of substantially linear elements along a pattern direction such that the incident direction of the diffracted light component provided to the further intermediate different element is within an angular range between 50 and 70 degrees relative to the pattern direction.
 18. The electronic device of claim 14, comprising a computer game device.
 19. The electronic device of claim 14, comprising a digital camera.
 20. The electronic device of claim 14, further comprising a communications unit for receiving signals containing information indicative of the image data, wherein the data processing unit is operatively connected to the communications unit for receiving the information.
 21. The electronic device of claim 20, comprising a mobile terminal. 